TY - GEN A1 - Starick, Tommy A1 - Schmidt, Heiko T1 - Stochastische Modellierung einer Methan/Luft Freistrahl-Flamme mit detaillierter Chemie T2 - 30. Deutscher Flammentag, Hannover-Garbsen, 28-29 September 2021 N2 - Die vorliegende Arbeit befasst sich mit der stochastischen Modellierung einer Methan/Luft Freistrahl-Flamme unter Verwendung des One-Dimensional Turbulence (ODT) Modells. Bei der untersuchten Cabra-Brennerkonfiguration handelt es sich um ein offenes System, bei welchem ein vorgemischter Methan/Luft Freistrahl von einer zentral angeordneten Düse in eine Umgebungsströmung aus heißen Verbrennungsgasen strömt. Das One-Dimensional Turbulence Modell ist ein stochastisches und abbildungsbasiertes Modell, welches die molekulare Diffusion und Reaktionskinetik durch sich zeitlich entwickelnde, deterministische Erhaltungsgleichungen berücksichtigt und entlang eines eindimensionalen Rechengebietes vollständig auflöst. Die Besonderheit von ODT liegt in der Modellierung der turbulenten Advektion über zufällig auftretende Wirbelereignisse, welche den fundamentalen Erhaltungseigenschaften unterliegen. Für die Abbildung der Methan/Luft Verbrennungschemie wird ein reduzierter Mechanismus mit 19 Spezies und 15 Reaktionen und ein detaillierter Mechanismus mit 53 Spezies und 325 Reaktionen eingesetzt. Die gezeigten vorläufigen ODT-Simulationsergebnisse der Methan/Luft Freistrahl-Flamme beinhalten Mittellinienprofile, radiale Profile, Streudiagramme und zweidimensionale Visualisierungen der Freistrahl-Flamme, welche mit einer zylindrischen Formulierung von ODT erzeugt wurden. Zu Vergleichszwecken werden die Simulationsergebnisse experimentellen Messungen gegenübergestellt. Obwohl die Simulation von reaktiven Freistrahl-Flammen keinen neuen Anwendungsfall von ODT darstellt, ist die akkurate Wiedergabe des sensiblen Zusammenspiels des zunächst unverbrannten Freistrahls mit der heißen Umgebungsströmung eine Herausforderung für das Modell. In der durchgeführten Studie konnte gezeigt werden, dass die mittels ODT erzeugten Statistiken eine beachtlich gute Übereinstimmung mit den Vergleichsdaten aufweisen. Im Hinblick auf die reduzierte Dimensionalität von ODT, die Qualität der erzielten Ergebnisse und die erforderliche Rechenleistung, stellt ODT ein attraktives Modell zur Simulation von turbulenten und reaktiven Strömungen dar. Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2021_Flammentag.pdf ER - TY - GEN A1 - Klein, Marten A1 - Freire, Livia S. A1 - Lignell, David O. A1 - Kerstein, Alan R. A1 - Schmidt, Heiko T1 - Ein stochastischer Ansatz zur Modellierung fluktuierender Oberflächenflüsse in turbulenten Grenzschichten T2 - Kurzfassungen der Meteorologentagung DACH N2 - Im Konferenzbeitrag wird auf die Formulierung des stochastischen Modells eingegangen und gezeigt, dass neben Scherspannungen auch Druck-, Coriolis- und Auftriebskräfte berücksichtigt werden können. Das Modell wird beispielhaft als unabhängiges, numerisches Werkzeug angewendet, um fluktuierende Oberflächenflüsse in turbulenten Kanalströmungen sowie stabilen und konvektiven Grenzschichten zu untersuchen. Es werden sowohl glatte, als auch raue bzw. bewachsene (poröse) Oberflächen betrachtet. Anhand neuer Ergebnisse wird demonstriert, dass der Modellansatz in der Lage ist, Referenzdaten zufriedenstellend zu reproduzieren und extrapolieren. Daneben werden aktuelle Arbeiten zur Kopplung des stochastischen Modellansatzes mit Large-Eddy-Simulationen vorgestellt. Es wird gezeigt, dass die stochastische Modellierung oberflächennaher, subgitterskaliger Schwankungen in der Lage ist, wandnahe Turbulenzspektren zu reproduzieren und den filterbasierten Modellfehler bei ansonsten fester Gitterauflösung zu verringern. KW - one-dimensional turbulence KW - stochastic modeling KW - turbulent boundary layer KW - turbulent convection KW - rotating and stratified flows Y1 - 2021 UR - https://meetingorganizer.copernicus.org/DACH2022/DACH2022-22.html U6 - https://doi.org/10.5194/dach2022-22 VL - 2022 SP - 1 EP - 1 PB - Copernicus ER - TY - GEN A1 - Kerstein, Alan R. A1 - Lignell, David O. A1 - Schmidt, Heiko A1 - Starick, Tommy A1 - Wheeler, Isaac A1 - Behrang, Masoomeh T1 - Using Hips As a New Mixing Model to Study Differential Diffusion of Scalar Mixing in Turbulent Flows T2 - 2021 AIChE Annual Meeting N2 - Mixing two or more streams is ubiquitous in chemical processes and industries involving turbulent liquid or gaseous flows. Modeling turbulent mixing flows is complicated due to a wide range of time and length scales, and non-linear processes, especially when reaction is involved. On the other hand, in turbulent reacting flows, sub-grid scales need to be resolved accurately because they involve reactive and diffusive transport processes. Transported PDF methods use mixing models to capture the interaction in the sub-grid scales. Several models have been used with varying success. In this study, we present a novel model for simulation of turbulent mixing called Hierarchical Parcel Swapping (HiPS). The HiPS model is a stochastic mixing model that resolves a full range of time and length scales with the reduction in the complexity of modeling turbulent reacting flows. This model can be used as a sub-grid mixing model in PDF transport methods, as well as a standalone model. HiPS can be applied to transported scalars with variable Schmidt numbers to capture the effect of differential diffusion which is important for modeling scalars with low diffusivity like soot. We present an overview of the HiPS model, its formulation for variable Schmidt number flows, and then present results for evaluating the turbulence properties including the scalar energy spectra, the scalar dissipation rate, and Richardson dispersion. These model developments are an important step in applying HiPS to more complex flow configurations. Y1 - 2021 UR - https://plan.core-apps.com/aiche2021/event/002309c77cf108fff1a6a8a101a07ebd ER - TY - GEN A1 - Starick, Tommy A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Stochastic Modeling of a Lifted Methane/Air Jet Flame with Detailed Chemistry T2 - Proceedings in Applied Mathematics & Mechanics N2 - This preliminary numerical study investigates a lifted methane/air jet flame in a vitiated coflow by means of the One-Dimensional Turbulence (ODT) model. In the considered Cabra Burner configuration [Combust. Flame 143 491-506 (2005)], a jet flame issues from a central nozzle into a vitiated coflow of hot combustion products from lean premixed hydrogen/air flames. ODT is a map-based model for turbulent flow simulations which uses a stochastic formulation for the turbulent advection. The diffusion and reaction effects along the one-dimensional domain are considered by temporally advancing deterministic evolution equations. ODT simulations are performed with a representation of the methane/air chemistry by a detailed 53-species mechanism with 325 reactions. In this work, we present centerline profile of temperature and species concentrations obtained from ODT simulations using a cylindrical ODT-formulation. Additionally, a two-dimensional rendering of the temperature distribution is shown. Although the simulation of reactive jet configurations by means of ODT is not novel, the complex stabilization region depending on the flow conditions represents a challenge for the model. Considering the reduced order of the model, ODT is able to predict the flow characteristics and reasonably matches the existing experimental data. Y1 - 2020 UR - https://onlinelibrary.wiley.com/doi/full/10.1002/pamm.202000316 U6 - https://doi.org/10.1002/pamm.202000316 SN - 1617-7061 VL - 20 IS - 1 ER - TY - GEN A1 - Starick, Tommy A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Stochastic Modeling of a Lifted Methane/Air Jet Flame with Detailed Chemistry T2 - 91th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 15-19, 2021 Kassel, DE Y1 - 2021 UR - https://onlinelibrary.wiley.com/doi/epdf/10.1002/pamm.202100237 U6 - https://doi.org/10.1002/pamm.202100237 ER - TY - GEN A1 - Xie, Tianxiao A1 - Starick, Tommy A1 - Mosgow, Anatol A1 - Berg, Heinz Peter A1 - Höschler, Klaus A1 - Schmidt, Heiko T1 - Thermofluiddynamic pre-design of a primary surface heat exchanger under the influence of heat radiation using 1D/3D coupled simulation method T2 - NAFEMS World Congress 2021, online, 25-29. Oktober 2021 N2 - Within the Framework of the "TurboFuelCell (TFC)" a highly integrated and compact energy conversion system based on Micro Gas Turbine Solid Oxide Fuel Cell (MGT-SOFC) hybrid process is being developed by the team at BTU-Cottbus Senftenberg. This work focuses on the extension of the pre-design process of a primary surface heat exchanger (PSHX), which is a key component for the coupling between MGT and SOFC, using an 1D/3D hybrid simulation method for the understanding of its behaviour under the influence of heat radiation. In a MGT-SOFC hybrid process the high temperature heat exchanger plays an important role in preheating the fresh air to a minimum operation temperature necessary for SOFC. Due to the special location of this PSHX in the TFC, it is constantly exposed to heat radiation from the SOFC module, which requires additional consideration of its influence for better model accuracy. A first design, which is later extended through an 1D Flow network model, based on 𝜖 − 𝑁𝑇𝑈 method is presented. A complete 3D-CFD simulation with consideration of heat radiation is initially employed for the whole flow process to examine the first design. However, this approach proves to be highly computationally expensive due to the large dimensional difference between the plenum for cathode exhaust air and the fine channels in the PSHX. To reduce the computational effort, the flow and heat transfer in the PSHX is modelled by 1D elements. The flow in the plenum is simulated by 3D-CFD, which better accounts for convection and thermal radiation. A comparison between 3D-CFD and 1D/3D hybrid model is performed. A significant reduction of simulation time and computing resources can be achieved for well calibrated hybrid model without compromising on accuracy. In the talk, the effect of insulation layer thickness variations on the heat transfer on the plenum side due to heat radiation and their influence on the heat exchanger efficiency are discussed. Consequently, design improvements are realized based on the previous findings. Finally, the 1D/3D hybrid simulation method is evaluated and prepared for the general applications in thermal management of machines based on coupled MGT-SOFC process. Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2021_NAFEMS_World_Congress_Manuscript.pdf UR - https://agenda.nwc21.org/session.php?s=B5 ER - TY - GEN A1 - Sharma, Sparsh A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Modelling turbulent jets at high-Reynolds number using one-dimensional turbulence T2 - AIAA AVIATION 2021 FORUM KW - stochastic modeling KW - turbulent round jet KW - one-dimensional turbulence Y1 - 2021 UR - https://arc.aiaa.org/doi/abs/10.2514/6.2021-2104 SN - 978-1-62410-610-1 U6 - https://doi.org/10.2514/6.2021-2104 PB - American Institute of Aeronautics and Astronautics, Inc. ER - TY - GEN A1 - Sharma, Sparsh A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Features of far-downstream asymptotic velocity fluctuations in a round jet: A one-dimensional turbulence study T2 - Physics of Fluids KW - stochastic modeling KW - turbulent round jet KW - one-dimensional turbulence KW - jet similarity KW - multi-scale fluctuation modeling Y1 - 2022 UR - https://aip.scitation.org/doi/10.1063/5.0101270 U6 - https://doi.org/10.1063/5.0101270 SN - 1089-7666 VL - 34 IS - 8 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Stochastic modeling of transient Ekman flow at arbitrary Reynolds number driven by horizontal bottom wall oscillation T2 - EMS Annual Meeting 2022, Abstracts KW - stochastic modeling KW - one-dimensional turbulence KW - rotating boundary layers KW - intermittency Y1 - 2022 U6 - https://doi.org/10.5194/ems2022-617 VL - 19 PB - Copernicus CY - Bonn, Germany ER - TY - GEN A1 - Tsai, Pei-Yun A1 - Schmidt, Heiko A1 - Klein, Marten T1 - Modeling simultaneous momentum and passive scalar transfer in turbulent annular Poiseuille flow T2 - 92nd Annual Meeting of GAMM KW - stochastic modeling KW - one-dimensional turbulence KW - heat and mass transfer KW - skin friction drag KW - forced convection KW - spanwise wall curvature Y1 - 2022 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2022_coaxialPipe_GAMM_abstract.pdf UR - https://jahrestagung.gamm-ev.de/wp-content/uploads/2022/08/Daily_Program_Web.pdf PB - Gesellschaft für angewandte Mathematik und Mechanik e.V. CY - Aachen, Germany ER -